Compositions containing high molecular weight poly(vinylamines) for enhanced oil recovery

ABSTRACT

The inverse emulsion polymerization of a monomer of the formula ##STR1## wherein R and R 1  represent hydrogen or a C 1  -C 4  alkyl group, using a surfactant system having a hydrophilic-lipophilic balance value from 4 to 9, an azo-type free radical initiator and certain hydrocarbon liquids to yield a water-in-oil emulsion of a homopolymer of at least 10 6  average molecular weight, the emulsion having a viscosity less than 10 cps, at 15% solids, 60 rpm Brookfield and 20° C. 
     Also disclosed is the preparation of poly(vinylamines) of at least 10 6  average molecular weight by acid or base hydrolysis of the homopolymer emulsion. 
     Also disclosed are enhanced oil recovery compositions, drilling mud compositions, cements for drilling holes, completion fluids, acidized fracturing fluids, and wet-end paper additives containing the poly(vinylamines) and demonstrating superior properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser.No. 914,046 filed Oct. 1, 1986.

TECHNICAL FIELD

The invention relates to the use of high molecular weightpoly(vinylamines) in enhanced oil recovery compositions.

BACKGROUND OF THE INVENTION

Water soluble polymers such as poly(N-vinylamides), frequently requirehigh molecular weight to develop satisfactory properties for highperformance applications. Low to medium molecular weightpoly(N-vinylformamide) and poly(N-vinylacetamide) have been prepared byconventional solution polymerization in water and alcohols usingoil-soluble and water-soluble initiators. However, poly(N-vinylamides)of high molecular weight are difficult to produce by conventionalsolution polymerization in that the polymer product obtained underuseful conditions is a gel which is difficult to handle. In addition,problems with high solution viscosity and poor heat transfer make suchsynthesis impractical on a commercial scale.

Nonetheless, it was believed by the present inventors that theapplications performance of poly(vinylamides) and poly(vinylamines)could be enhanced by the preparation and use of homopolymers of veryhigh molecular weight (>10⁶).

U.S. Pat. No. 4,500,437 discloses acrylamide copolymers and terpolymerscontaining N-vinylformamide and N-vinylacetamide prepared by inverseemulsion polymerization in Examples 67-70 with the polymers of Examples68 and 70 having a molecular weight below 100,000; i.e <10⁵. Example 20shows the preparation of poly(vinylformamide) by solutionpolymerization.

U.S. Pat. No. 4,421,602 discloses linear basic polymers containing from90 to 10 mole% of copolymerized vinylamine units and from 10 to 90 mole%of copolymerized N-vinylformamide units. This patent teaches that thepolymers can be prepared by solution polymerization in water, awater-soluble solvent or a mixture of water and a water-soluble solventand actually shows such solution polymerization in the examples. It issuggested that the polymerization can also be carried out as awater-in-oil emulsion polymerization in a water-immiscible solvent, butthere are not examples of such polymerization.

U.S. Pat. No. 4,018,826 discloses the preparation of poly(vinylamine)salts of mineral acids by polymerizing vinylacetamide with a freeradical polymerization catalyst, and hydrolyzing thepoly(vinylacetamide) to the desired amine salts by contacting thepoly(vinylacetamide) with an aqueous solution of the correspondingmineral acid. Poly(vinylamine) product of about 3,000 to about 700,000molecular weight (4,000 to about 1,000,000 for the salt product) issuggested.

U.S. Pat. No. 3,558,581 discloses homo- and copolymers ofN-vinyl-N-methylamine by hydrolysis of the corresponding polymers ofN-vinyl-N-methylformamide with mineral acids.

U.S. Pat. No. 3,597,314 discloses a water-soluble polymer consistingessentially of units derived from N-vinyl-N-methylformamide having60-100% of the formic acid radicals of the polymer split off by acidhydrolysis. There is no disclosure regarding inverse emulsionpolymerization.

GB No. 2,152,929 is directed to a process for producing N-substitutedformamides for use in producing N-vinylformamide by thermallydecomposing N-(alpha-alkoxyethyl)formamide in the gas phase. It issuggested that the N-vinylformamide can be bulk polymerized, solutionpolymerized using an aqueous solution or an organic solution, oremulsion polymerized singly or together with a monomer usedconventionally for producing water-soluble polymers suitable for makingflocculants, in the presence of a polymerization initiator of azocompounds. The thus obtained poly(vinylformamide) is hydrolyzed underacidic or basic conditions to obtain a cationic polymer ofpoly(vinylamines).

D. J. Dawson, et al., "Poly(vinylamine hydrochloride). Synthesis andUtilization for the Preparation of Water-Soluble Polymeric Dyes," J. Am.Chem. Soc., 98: 19, 5996 (1976) discloses the preparation ofN-vinylacetamide and its polymerization in solution followed by acidhydrolysis to poly(N-vinylamine hydrochloride).

Representative of the numerous prior art references relating towater-in-oil emulsion polymerization of water-soluble monomers are thefollowing patents: U.S. Pat. Nos. 2,982,749; 3,278,506; 3,284,393;3,957,739; 3,975,341; 4,078,133; and 4,312,969.

R. H. Summervile, et al., "Synthesis of N-vinyl Acetamide andPreparation of Some Polymers and Copolymers," Polym. Reprints, 24, 12(1983) discloses that the inverse emulsion polymerization ofN-vinylacetamide initiated by sodium persulfate in water and cyclohexaneusing Igepal surfactants was tried without success.

U.S. Pat. No. 4,217,214 discloses that polyvinylamine hydrochloridehaving a molecular weight of about 5×10⁵ or greater has been found to beparticularly effective as a flocculating agent in wastewater systems.The examples disclose the use of a poly(vinylamine) hydrochloride havinga molecular weight of 2×10⁶ and state that the poly(vinylamine)hydrochloride used is prepared as described in U.S. Pat. No. 4,018,826.

U.S. Pat. No. 4,623,699 discloses linear, basic polymer powders whichcontain units of the formula --CH₂ --CH(NH₂)-- and have a Fikentscher Kvalue from 10 to 200 prepared by eliminating the formyl groups fromN-vinylformamide polymer powders with a gaseous hydrogen halide in thepresence of not more than 5% by weight, based on the polymer used, ofwater.

JP No. 61/141712 discloses a method for producing N-vinylcarboxylic acidamide polymers by a procedure in which an aqueous solution ofN-vinylcarboxylic acid amide is dispersed in a hydrocarbon-typedispersing medium using an oil-soluble polymer dispersion stabilizerfollowed by radical polymerization.

SUMMARY OF THE INVENTION

According to the present invention, very high molecular weightpoly(N-vinylamides) can be prepared by an inverse emulsionpolymerization process. The present invention provides an inversehomopolymer emulsion consisting essentially of 10-70 wt% of an aqueoussolution containing 10-90 wt% of a homopolymer of an N-vinylamide of theformula ##STR2## wherein R and R¹ represent hydrogen or a C₁ -C₄ alkylgroup, colloidally dispersed in a hydrocarbon liquid which is a C₅ -C₁₀alkane and, in addition, toluene and xylene when R=alkyl, a xylenecompound, the homopolymer being at least 10⁶ average molecular weightand the emulsion possessing a viscosity less than 10 cps at 15% solids,60 rpm Brookfield (7.9 sec⁻¹) and 20° C.

The method for preparing the inverse, or water-in-oil, emulsion involvescolloidally dispersing an aqueous solution containing 10-90 wt%water-soluble N-vinylamide of the above formula in the hydrocarbonliquid using a surfactant having an HLB value from 4 to 9, the weightratio of monomer-containing aqueous solution to hydrocarbon liquid beingpreferably in the range from 1:2 to 2:1, and polymerizing the monomerusing an azo-type free radical initiator.

The resultant very high molecular weight polymer emulsion has a lowviscosity ranging from 2 to less than 10 cps at 15% solids, 60 rpmBrookfield and 20° C., thus eliminating problems of solution viscositywhich arise when the polymer is prepared by a solution polymerizationprocess. In addition, the low viscosity homopolymer emulsion is easy tohandle and can be used directly.

One such use of the vinylamide homopolymer emulsions is in thepreparation of vinylamine homopolymers of at least a 10⁶ averagemolecular weight by acid or base catalyzed hydrolysis of thehomopolymer, preferably as the emulsion. The use of the mineral acid inthe hydrolysis step or in acidifying the base hydrolysis productprovides the poly(vinylamine) as the salt of such acid.

The very high molecular weight, water-soluble poly(N-vinylamides) andthe derived poly(vinylamines) have applications in the fields of watertreatment, enhanced oil recovery and papermaking. For example, thederived poly(vinylamines) can be used as an important component in oilfield chemical compositions such as drilling mud compositions, cementsfor drilling holes, completion fluids, and acidized fracturing fluids.Solution rheology (thickening efficiency and viscosity response to shearrates in the range of 1 to 1,000 sec⁻¹) of the poly(vinylamines) at a0.5 to 1% concentration in low level salt solutions, e.g. 2% KClsolution, is important in oil field chemical compositions for manyapplications. The very high molecular weight of the polymers affordsbetter viscosifying and rheology.

In enhanced oil recovery (EOR) applications the poly(vinylamines) of theinvention provide compositions having improved viscosity stability at90° C. and improved viscosity retention in sea water. Most commerciallyavailable polymers fail under both these conditions. Hydrolyzedpolyacrylamides fail in sea water solution at elevated temperatures dueto precipitation of the polymer in the presence of calcium ions in thesea water. Xanthan polymer is insensitive to calcium ions. However, athigh temperatures the polymer chains uncoil and lose their viscosifyingefficiency.

In general such EOR compositions would comprise sea water containingabout 1000 to 2000 ppm of the poly(vinylamine) and have a 10 to 20 cpsBrookfield viscosity at 7.9 sec⁻¹ (60 rpm) and 90° C. Very highmolecular weight vinylamine polymers according to the invention seem toshow improved stability at high temperature and calcium salinity--a setof conditions useful in high temperature EOR viscosifying applications.

When used in acidized fracturing fluids, the poly(vinylamines) of theinvention result in improved viscosity stability in concentratedhydrochloric acid solution at 70° C. Most commercial cellulosic polymerscurrently used in this application fail due to the breakdown of thepolymer backbone under these conditions. Such fluids comprise about 0.2to 2% poly(vinylamine) and 5 to 28% aqueous hydrochloric acid and have aFANN 35 viscosity of 10 to 100 cps at 300 rpm, 510 sec⁻¹ and R₁ B₁sensor.

Thus there is also provided a process for well stimulation by fractureacidizing with an aqeuous acidic solution wherein the acidic solution isinjected into the well to contact a formation under pressure sufficientto fracture the formation, the acidic solution containing as aviscosifier a vinylamine homopolymer having a molecular weight greaterthan 10⁶.

A further embodiment of the present invention is a drilling mudcomposition with good rheology. Such drilling mud compositions comprise0.1 to 1 wt% poly(vinylamine), 0 to 10 wt% salt and 0.5 to 5 wt% claydispersed in water.

Also provided by the invention are completion fluids exhibiting highviscosity in saturated brine solution as well as high temperatureviscosity stability. A typical completion fluid comprises a saturatedsalt solution containing 0.2 to 2 wt% poly(vinylamine).

The present invention also provides an increase in retention, drainagerate and flocculation in a papermaking process comprising the depositionof a pulp stock to form a nonwoven sheet by adding to the pulp stockpoly(vinylamines) according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Poly(N-vinylamides) of molecular weight at least 10⁶, preferably 3×10⁶to 15×10⁶, are prepared via an inverse emulsion polymerization processby reacting the following composition under an inert atmosphere:

1. water-soluble N-vinylamide monomer,

2. water,

3. hydrocarbon liquid,

4. water-in-oil emulsifying agent, and

5. a nitrogen-containing free radical initiator.

The aqueous solution comprising the first two components contains 10 to90 wt%, preferably 50 to 70 wt%, of a water-soluble N-vinylamide of theformula ##STR3## where R and R¹ represent hydrogen or an alkyl grouphaving 1-4, preferably 1-2, carbon atoms, especially a methyl group. Theweight ratio of monomer-containing aqueous solution to hydrocarbonliquid may be varied widely depending upon the monomer used, butpreferably is about 1:2 to 2:1.

The suitable hydrocarbon liquids for use in the invention are immisciblewith water and do not significantly dissolve the monomers in thepresence of water. Such hydrocarbon liquids are exemplified by acyclicand cyclic C₅ -C₁₀ alkanes such as hexane, octane, decane, anddecahydronaphthalene (decalin) and, in addition, certain aromatichydrocarbons for N-vinylacetamides and the aromatic hydrocarbons tolueneand xylene. Contemplated as the functional equivalent of toluene andxylene when R is an alkyl group in the monomer formula are ethylbenzeneand tetrahydronaphthalene (tetralin). The preferred hydrocarbon liquidsare the C₅ -C₁₀ acyclic alkanes.

The stabilizing system comprises suitable emulsifying agents, orsurfactants, having a hydrophilic-lipophilic balance (HLB) value from 4to 9, preferably 4 to 7.5, and include sorbitan fatty acid esters suchas sorbitan monostearate, oleate, laurate or palmitate;polyoxyethylenesorbitan fatty acid esters, i.e. reaction products of onemole of the aforementioned sorbitan fatty acid esters with from 4 to 40moles of ethylene oxide; polyoxyethylene sorbitol esters of fatty acids;and mixtures thereof. The preferable quantity of surfactant is 5 to 20wt% based on the monomer-containing aqueous solution.

The free radical initiator should be one of the azo compounds well knownin the polymerization art such as 2,2'-azobis(isobutyronitrile);2,2'-azobis(2-amidinopropane)hydrochloride;4,4'-azobis(4'-cyanopentanoic acid) and the like. Persulfates andhydrogen peroxide have been found not to be suitable in practicing theinvention. Redox catalyst systems may also be used comprising the azoinitiators with a reducing agent typically used in the art. The amountof free radical initiator can be varied widely depending upon reactiontemperatures, rate of polymerization, degree of polymerization to beobtained, but preferably is in the range of 0.001 to 0.5 mole% of themonomer used.

The polymerization is usually carried out under an inert atmosphere,preferably under nitrogen. The reaction temperature is preferably in therange of 40°-60° C. A high temperature, i.e. >60° C., may cause sidereactions unfavorable to the polymer such as crosslinking or chaintransfer. A lower temperature may be impractical because of longreaction times.

The homopolymer product can be isolated from the emulsion by adding aflocculating agent and filtering. The precipitated product is thenwashed and dried. Generally, a polar organic solvent which is a goodsolvent for the surfactant but a poor solvent for the polymer, e.g.acetone, is used to aggregate the polymer. The precipitated polymer isfiltered and washed to remove the surfactant. The dried and purifiedpolymer of very high molecular weight is in the form of a fine powderand is water soluble.

The vinylamide homopolymer products are hydrolyzed to vinylaminehomopolymers of at least 10⁶ average molecular weight in the presence ofacids or bases. More desirably, vinylamine homopolymers of 1.8×10⁶ to9×10⁶ molecular weight or more are obtained. The vinylamine polymerssuitable for use in enhanced oil recovery compositions are greater thanabout 50% hydrolyzed, preferably greater than about 90%, to about 99+%hydrolyzed.

Suitable acids for the hydrolysis include mineral acids such ashydrochloric, hydrobromic, sulfuric, phosphoric and perchloric acid; andorganic acids such as trifluoroacetic acids and methanesulfonic acid.The bases which can be employed include alkali and alkaline earthhydroxides such as sodium hydroxide, potassium hydroxide, calciumhydoxide and barium hydroxide; and quaternary ammonium hydroxides suchas tetramethyl ammonium hydroxide. The quantity of the acid or baserequired may vary widely, depending upon the degree of hydrolysisdesired and reaction conditions. Approximately, 1 to 3 equivalents ofthe acid or base per equivalent of the polymer is preferred to achieveessentially complete hydrolysis.

The hydrolysis can be performed in various solvents, including water;liquid ammonia; alcohols such as methanol, ethanol, isopropanol, andt-butanol; amines such as methylamine, dimethylamine, ethylamine and thelike; and hydroxy amines such as ethanolamine. However, it is muchpreferred to simply add the acid or base in water to the water-in-oilemulsion.

The temperature of the hydrolysis may range from 20° to 200° C.depending upon the type of polymer and hydrolysis employed. Generally,hydrolysis proceeds more rapidly for poly(N-vinylformamide) than forpoly(N-vinylacetamide). Thus, hydrolysis of poly(N-vinylformamide) canbe carried on under milder conditions, i.e. at lower temperatures andshorter reaction times than for poly(N-vinylacetamide). The preferabletemperature range of a base hydrolysis is 70° to 100° C. which is lowerthan that of acid or base hydrolysis of N-vinylacetamide in the range of110° to 200° C.

The hydrolyzed polymer products thus obtained comprise the repeatingfree amino-containing units of the formula ##STR4## in the case of basehydrolysis, and amino-containing units of the formula ##STR5## in thecase of acid hydrolysis, where X⁻ represents the anion corresponding tothe acid employed in the hydrolysis.

Poly(vinylamine) is preferably isolated in the salt form to preventadsorption of atmospheric carbon dioxide. The polymer salt is isolatedby acidifying the hydrolysis mixture to cause the polymer toprecipitate. The precipitated polymer generally is a gum, but a fibrousmaterial can be obtained after redissolving, followed by reprecipitationin methanol.

The products of this invention are high molecular weightpoly(N-vinylamides), especially poly(N-vinylformamide) of 3-15×10⁶ molwt and poly(N-vinylacetamide) of 1.3-5×10⁶ mol wt, and the derivedpoly(vinylamine) and poly(vinylamine) salts.

These polymeric materials, which may also contain up to 25 wt%co-polymerizable monomers, such as, for example, acrylamide and N-vinylpyrrolidone, provided the polymer maintains sufficient water solubility,are particularly useful as flocculants, retention agents, and thickenersin the areas of water treatment, enhanced oil recovery and papermaking.These polymers may also be used as corrosion inhibitors, photographicchemicals, surfactants, protein hardeners, ion exchange resins, and asingredients in the preparation of drugs, food dyes, herbicides andpesticides.

With regard to enhanced oil recovery (EOR), such EOR compositions wouldcomprise 500 to 2500 ppm, preferably 1000 to 2000 ppm, and mostdesirably about 1500 ppm of a high molecular weight poly(vinylamine) insea water. The poly(vinylamine) should have an average molecular weightof at least 10⁶, preferably 1.8-9×10⁶. The composition should have aBrookfield viscosity at 7.9 sec⁻¹ (60 rpm) and 90° C. of 5 to 25 cps,preferably 10 to 20 cps. The sea water may be a synthetic aqueouscomposition, i.e. 3% sodium chloride and 0.3% calcium chloride in waterat pH 6.

EXAMPLE 1

This Example shows a preparation of a very high molecular weightpoly(N-vinylformamide) by inverse emulsion polymerization.

Sorbitan monostearate (SPAN 60 surfactant, HLB 4.7, 2.5 g) was dissolvedin octane (90 g) and the resulting solution was transferred to areaction kettle. The reactor was purged with nitrogen and kept in anitrogen atmosphere throughout the polymerization. The N-vinylformamidesolution (15 g in 30 g of water) was degassed and added to the reactorat the rate of 2.5 ml/min with vigorous agitation. (The N-vinylformamidewas purified by vacuum distillation at 70° C., 1 torr, prior to use.)While the reaction mixture was heated to 50° C.,2,2'-azobis(2,4-dimethylpentanitrile) (Vazo 52 initiator, 0.05 g) wascharged. After 3 hours at 50° C. with agitation, a stable polymericemulsion was produced having a viscosity of 3 cps. The solid polymerproduct was recovered by breaking the emulsion by the addition ofacetone. The isolated N-vinylformamide homopolymer had a molecularweight of 6.7×10⁶ as measured by light scattering and a viscosity of21,000 cps as a 5% aqueous solution.

EXAMPLE 2

The vinylformamide homopolymer (10 g) of Example 1 was dissolved inwater (990 g) and then mixed with 50% aqueous sodium hydroxide (11.3 g).The resulting mixture was heated for 8 hours at 80° C. under a nitrogenatmosphere. To the reaction mixture was added concentrated hydrochloricacid until the polymer precipitated. The acid solution was decanted. Theprecipitated polymer was redissolved in water and reprecipitated withmethanol. The vinylamine homopolymer hydrochloride salt had a viscosityof 400 cps at 1% aqueous solution.

EXAMPLE 3

This Example shows the preparation of a very high molecular weightpoly(N-vinylacetamide) by inverse emulsion polymerization.

The N-vinylacetamide was prepared according to the method taught in U.S.Pat. No. 4,018,826. The N-vinylacetamide was purified as follows: Thecrude N-vinylacetamide (1 kg) was flash distilled at 70°-74° C., 1 torr.Approximately two-thirds of the material was distilled to give a 70:30N-vinylacetamide/acetamide mixture. This mixture (100 g) and toluene(600 g) were placed in a 1000 ml beaker and the resulting mixture wasstirred well. The yellow toluene solution was decanted from insolublesolids which were washed twice with 50 g of fresh toluene. The toluenesolutions were combined and washed with 25 g of brine. The yellow brinesolution was discarded. The toluene solution was then extracted fourtimes with 130 ml of water. The aqueous solution was back extracted with25 ml of methylene chloride. The methylene chloride solution wasdiscarded. The aqueous solution was saturated with sodium chloride andextracted four times with 330 ml methylene chloride. After removing themethylene chloride under reduced pressure, 42 g of pure N-vinylacetamide(60% recovery) was obtained.

A mixture of N-vinylacetamide (15 g), water (45 g), xylene (90 g), andSPAN 60 surfactant (4 g) was polymerized in the same manner as describedin Example 1, using 2,2'-azobis(2-methylpropionitrile) AIBN (0.08 g) asan initiator. The N-vinylacetamide homopolymer was precipitated byaddition of acetone, and had a molecular weight of 1.5×10⁶, asdetermined by gel permeation chromatography.

EXAMPLE 4

The N-vinylacetamide homopolymer of Example 3 (10 g) was dissolved inwater and mixed with concentrated hydrochloric acid (2 moleequivalents). The resulting mixture was heated to reflux (about 110° C.)for 48 hours. To the reaction mixture was added concentratedhydrochloric acid until the polymer precipitated. The acid solution wasdecanted. The precipitated polymer was redissolved in water andreprecipitated with methanol yielding 8.8 g of product having aviscosity of 324 cps as a 1% aqueous solution.

EXAMPLES 5-9

N-vinylformamide (NVF) was polymerized in the same manner as describedin Example 1. The data regarding the polymerization recipes and theresulting emulsions are set forth in Tables 1 and 2, respectively.

                                      TABLE 1                                     __________________________________________________________________________    EXAMPLE                                                                              NVF (g)                                                                            WATER (g)                                                                            HYDROCARBON (g)                                                                           SPAN 60 (g)                                                                          VAZO 52 (g)                                                                          ADDITIVE (g)                     __________________________________________________________________________    5      15   30     Octane 55   2.5    0.05   --                               6      15   30     Octane 55   2.5    0.05   0.25 Vinol 125                   7      15   10     Octane 75   2.5    0.05   --                               8      15   30     Hexane 90   2.5    0.05   --                               9      15   30     Hexane 90   2.5    0.05   0.25 Poly(vinylamine)            __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                                 EMULSION       HOMOPOLYMER                                           EXAMPLE  VISCOSITY (cps)                                                                              MOLECULAR WEIGHT                                      ______________________________________                                        5        4              7 × 10.sup.6                                    6        4              7 × 10.sup.6                                    7        4              6 × 10.sup.6                                    8        4              6 × 10.sup.6                                    9        4              6 × 10.sup.6                                    ______________________________________                                    

EXAMPLE 10

In this example the inverse emulsion polymerization of N-vinylformamideaccording to Example 1 was attempted using toluene, xylene and keroseneindividually as the hydrocarbon liquid phase. In each instance a highmolecular weight N-vinylformamide polymer was obtained, but theemulsions were unstable and broke.

EXAMPLE 11

This example shows the need to use an azo-type initiator. Following theprocedure of Example 1 using sodium or ammonium persulfate as theinitiator resulted in failure in that no polymer was obtained. Thisfailure is believed due to a possible redox reaction occurring betweenthe monomer and the persulfate.

EXAMPLE 12

In this example poly(N-vinylformamide) was prepared according to thesolution polymerization procedure of Example 12 in U.S. Pat. No.4,421,602. The isolated polymer was determined as having a molecularweight of 1.4×10⁵ by aqueous gas phase chromatography (GPC).

EXAMPLE 13

A poly(N-vinylformamide) emulsion was prepared according to theprocedure of Example 69 in U.S. Pat. No. 4,500,437. The resultantpolymer emulsion was paste-like and unstable. The isolatedpoly(N-vinylformamide) had a molecular weight of 5.1×10⁵ as determinedby aqueous GPC.

EXAMPLE 14

The polymerization of N-vinylformamide was performed according to theprocedure of Example 20 in U.S. Pat. No. 4,500,437. The product was aviscous liquid indicating a molecular weight of less than 5×10³.

EXAMPLE 15

This Example shows the application of a poly(vinylamine) according tothe invention in enhanced oil recovery. Two vinylamine homopolymers andtwo commercially available polymers, namely xanthan and a hydrolyzedpolyacrylamide, were evaluated at 1500 ppm in synthetic sea water usinga low shear Brookfield viscosity at 7.9 sec⁻¹.

                  TABLE 3                                                         ______________________________________                                        Low Shear Rheology in Sea Water.sup.a                                                      Conc  Brookfield Viscosity (cps).sup.b                           Polymer        (ppm)   R.T.       90° C.                               ______________________________________                                        Vinylamine (7 MM)                                                                            1500    16         13                                          Vinylamine (0.6 MM)                                                                          1500     6         2                                           Xanthan XC (2 MM)                                                                            1500    50         4                                           Hydrolyzed     1500    15         3                                           Polyacrylamide (2 MM)                                                         ______________________________________                                         .sup.a Sea Water = 3% NaCl + 0.3% CaCl.sub.2 ; pH = 6                         .sup.b Model LVF, 7.9 sec.sup.-1                                         

It can be seen from Table 3 that the vinylamine homopolymer of about7×10⁶ molecular weight outperformed the commercially available polymersas well as the lower molecular weight poly(vinylamine). The vinylaminehomopolymer demonstrated much improved viscosity stability at theelevated (90° C.) temperature compared to the other polymers.

EXAMPLE 16

In this Example the very high and the low molecular weight vinylamine(VAm) homopolymers were compared with guar for use in a fractureacidizing composition. The polymer concentration was 0.5% and theviscosity was measured using a FANN 35 viscometer, R₁ B₁ sensor at 510sec⁻¹.

                  TABLE 4                                                         ______________________________________                                        Fracture Acidizing                                                            Room Temperature    70° C. - 3 HR                                            VAm      VAm            VAm    VAm                                      % HCl (0.6 MM) (7 MM)   Guar  (0.6 MM)                                                                             (7 MM) Guar                              ______________________________________                                         0    28       129      37    18     68     34                                10    10       22       26    3      12.5   2                                 15     6       6.5      11    2      9      2                                 ______________________________________                                    

The 7 million molecular weight vinylamine homopolymer had the higherviscosity behavior compared to the lower molecular weight homopolymerand also outperformed the commercially available control, i.e. guar, athigher temperature.

EXAMPLE 17

In this Example the enhanced performance of a drilling mud containing avinylamine homopolymer of the invention was demonstrated.

A typical drilling mud formulation can be prepared as follows:

Clay Dispersion A:

11.1 g Aqua Gel Gold Seal Bentonite Clay

8 g Potassium chloride

400 g Water

Clay is dispersed to hydrate overnight.

Polymer Solution B:

2 g of polymer are dissolved in 400 g water, mixed for 2 to 4 hours andpH adjusted to 6.

Dispersion A (200 g) is added to polymer solution B (200 g) and mixedfor 4 hours. Rheology measurements were made using a FANN-35 viscometerat 300 and 600 rpm using standard API procedure.

                  TABLE 5                                                         ______________________________________                                                   Apparent Plastic           Yield                                              Viscosity                                                                              Viscosity                                                                              Gel Strength                                                                           Point                                   Polymer    (cps)    (cps)    10 sec/10 min                                                                          lb/100 ft.sup.2                         ______________________________________                                        VAm (80 M) 3.7      2.5      0        2.5                                     VAm (0.6 MM)                                                                             6.0      4.5      0        3.0                                     VAm (7 MM) 14.0     11.0     3/4      6.0                                     Xanthan (2 MM)                                                                           8.8      5.5      3/4      6.5                                     ______________________________________                                    

Table 5 shows that the very high molecular weight vinylamine homopolymerhad the best performance at room temperature.

EXAMPLE 18

The high molecular weight vinylamine homopolymer demonstrated asurprisingly high viscosity in saturated brine solutions. This propertyis important in completion fluids used in oil wells.

The saturated salt solution was prepared by mixing 1 g of a polymer into100 g of saturated salt solution and measuring the viscosity.

                  TABLE 6                                                         ______________________________________                                                   Viscosity in Saturated Salt Solution (cps)                         Polymer      NaCl          CaCl.sub.2                                         ______________________________________                                        VAm (0.6 MM) 3             100                                                VAm (7 MM)   11.5          300                                                Hercules 250 4             250                                                HHR (2-4 MM)                                                                  Hydroxyethylcellulose                                                         ______________________________________                                    

EXAMPLE 19

This Example demonstrates the use of the vinylamine homopolymer as a drystrength additive in paper making application.

Paper chromatography grade stock of uniform size was immersed in water,metered through squeeze rolls and weighed. Water pick-up was calculatedand determined consistent from sheet to sheet. The weight of polymerrequired per unit water volume to impart 0.5% polymer pick-up on sheetweight (dry/dry) was determined.

The low molecular weight (80M) vinylamine homopolymer and polyvinylalcohol were applied at 0.75%. The high molecular weight (7MM)vinylamine homopolymer which was an extremely high 3200 cps in viscositywas diluted to 0.188% solids and assumed to be 0.125%, the add-on levelof the others. The polymers were adjusted to pH 4.5 prior to sheetsaturation.

                  TABLE 7                                                         ______________________________________                                        Polymer     Instron Tensile                                                                           Mullen Burst                                          Saturant    lb/in       lb/in.sup.2                                                                              Tear CMD                                   ______________________________________                                        Blank       11.5        0.6        71                                         VAm (80 M)  13.5        2.5        77                                         VAm (7 MM).sup.a                                                                          14.5        3.1        89                                         VINOL 107 PVOH.sup.b                                                                      12.5        2.0        80                                         (60 M)                                                                        ______________________________________                                         .sup.a 0.125% addon compared to 0.5% for the others.                          .sup.b Polyvinyl alcohol marketed by Air Products and Chemicals. Inc.    

It can be seen that the very high molecular weight vinylaminehomopolymer was an effective dry strength additive in papermaking at 1/4the dosage compared to the low molecular weight vinylamine homopolymer.

EXAMPLE 20

This Example shows the retention characteristics of the vinylaminehomopolymer in papermaking.

Immediately prior to hand sheet preparations, softwood and hardwoodbleached kraft pulps were each suspended at 1.5% consistency indeionized water. The pulps were then blended 1:1 by weight and an amountequivalent to 30 g (oven dry basis) was utilized in preparing each setof hand sheets. Ten percent of anatase TiO₂ based on fiber weight wasadded followed by 5 minutes of stirring. (The TiO₂ was predispersed at10% solids in deionized water). Sufficient pulp to form a 2.5 g handsheet was removed and treated with polymer followed by 30 seconds ofmoderate stirring. The treated fiber suspension was then added to aNoble and Wood sheet mold containing sufficient deionized water toprovide a forming consistency of 0.04%. Hand sheets formed from thefiber suspensions were pressed 5 minutes at 50 psig between blotterstock and then drum dried 7 minutes at 220° F. in contact with oneblotter.

Following this procedure the polymers were added to the fiber suspensionat 0.5% consistency at addition levels of 0, 0.01, 0.05, 0.1, 0.2 and 1%based on fiber. The pH was maintained at 5. Hand sheets prepared in themanner described were conditioned at 50% RH and 73° F. and tested forfiller retention using the TAPPI standard method.

                  TABLE 8                                                         ______________________________________                                        Polymer               % TiO.sub.2 Retention                                   ______________________________________                                        VAm (7 MM)            93.1                                                    VAm (80 M)            83.3                                                    Hercules 834 Heterofloc                                                                             85.6                                                    High Mol. Wt./High Charge Density,                                            PAM (2-4 MM)                                                                  Allied Colloid DSR 1256                                                                             54.0                                                    Low Mol. Wt./Low Charge Density,                                              PAM (<1 MM)                                                                   ______________________________________                                         PAM = Polyacrylamide                                                     

It can be seen that the 7MM molecular weight poly(vinylamine)demonstrated a superior TiO₂ retention at 0.1-0.2% addition level towood pulp.

STATEMENT OF INDUSTRIAL APPLICATION

The present invention provides very high molecular weightpoly(N-vinylamides) by inverse emulsion polymerization and derivedpoly(vinylamines) having applications in water treatment, enhanced oilrecovery and papermaking fields.

We claim:
 1. An enhanced oil recovery composition consisting essentiallyof sea water containing 500 to 2500 ppm by weight poly(N-vinylamide) ofat least 10⁶ average molecular weight and greater than 50% hydrolyzed tovinylamine units, the composition having a 5 to 25 cps Brookfieldviscosity at 7.9 sec⁻¹ and 90° C.
 2. The composition of claim 1 whichcontains 1000 to 2000 ppm by weight hydrolyzed poly(vinylamide).
 3. Thecomposition of claim 1 in which the poly(vinylamide) has a 3 to 15×10⁶average molecular weight before hydrolysis.
 4. The composition of claim1 which has a 10 to 20 cps Brookfield viscosity.
 5. The composition ofclaim 2 in which the poly(vinylamide) has a 3 to 15×10⁶ averagemolecular weight before hydrolysis.
 6. The composition of claim 5 inwhich the poly(vinylamide) is greater than about 90% hydrolyzed.
 7. Thecomposition of claim 6 which has a 10 to 20 cps Brookfield viscosity. 8.The composition of claim 7 in which the hydrolyzed poly(vinylamide) isabout 1.8 to 9×10⁶ average molecular weight.
 9. In an enhanced oilrecovery composition comprising sea water containing a polymer forviscosifying, the improvement which comprises as the viscosifyingpolymer a poly(vinylamide) of at least 10⁶ average molecular weight andgreater than about 90% hydrolyzed to vinylamine units.
 10. Thecomposition of claim 9 in which the poly(vinylamide) is 3 to 15×10⁶average molecular weight before hydrolysis.
 11. The composition of claim9 in which the hydrolyzed poly(vinylamide) is about 1.8 to 9×10⁶ averagemolecular weight.
 12. The composition of claim 9 in which thepoly(vinylamide) is about 99+% hydrolyzed.
 13. The composition of claim10 in which the poly(vinylamide) is about 99+% hydrolyzed.